Abstract
AbstractIn this work, the effect of an expansin‐like cerato‐platanin (CP) protein as a pre‐treatment for the enzymatic hydrolysis of bacterial cellulose (BC) is investigated. To this scope, cellulases from Trichoderma reesei are used as hydrolyzing agent using different enzyme/BC formulations. Turbidity experiments reveal that for the higher enzyme concentrations (formulations 0.5:1 and 1:1) the enzymatic hydrolysis of BC show similar hydrolysis kinetics and is not dependent of the CP. However, at higher BC concentrations (formulations 0.25:1 and 0.33:1), the hydrolysis of BC is hindered by the non‐catalytic protein, as confirmed by the lower content of cellobiose and glucose in the presence of CP. Light scattering experiments show that the addition of CP led to an increase of the BC particle size from (445–630 nm) to (890–1.26 μm) for the formulation 1:1, which is also corroborated by atomic force microscopy and transmission electron microscopy analyses. These results suggest that CP did not positively affect the hydrolysis of BC, in contrast to what was previously observed for plant‐derived cellulose. This work for the first time investigates the anomalous behavior of cerato platanin family members with regard to its loosening activity on the structure of bacterial cellulose.
Highlights
Cerato-platanins are proteins produced exclusively by fungi and belong to a protein family discovered 20 years ago (Cerato platanin family―CPF).[1]
Turbidity experiments were used to investigate the extent of the enzymatic hydrolysis of bacterial cellulose (BC) both in the presence and in the absence of CP
Previous work showed that a decrease in turbidity over time was a consequence of the size reduction of the BC fibrils down to the nanoscale level, which reduced the light scattering in the BC aqueous solution.[25]
Summary
Cerato-platanins are proteins produced exclusively by fungi and belong to a protein family discovered 20 years ago (Cerato platanin family―CPF).[1]. The addition of cellulose-binding domains (CBDs) from cellulases in cellulose-rich materials, were successfully used as a biological pre-treatment step in the glucose conversion process of the fibrous substrate, making it less recalcitrant for the subsequent enzymatic hydrolysis.[27] Similar results were obtained combining the effect of white rot fungi and liquid hot water as a biomass pre-treatment.[28] As reported in literature, when compared with the other cited methods (e.g., high energy radiation, alkaline or acid methods), biological pre-treatments exhibit extra benefits being considered both an environmental friendly (mainly due to the limited energy consumption) and an economically viable process.[29]. To the best of our knowledge, the assessment of the expansin-like activity of ceratoplatanins on cellulose of bacterial origin has never been reported before
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